U.S. patent number 4,529,072 [Application Number 06/357,535] was granted by the patent office on 1985-07-16 for automatic clutch control system.
This patent grant is currently assigned to Aisin Seiki Kabushikikaisha. Invention is credited to Kouichiro Hirosawa, Tsutomu Mitsui, Tomio Oguma.
United States Patent |
4,529,072 |
Oguma , et al. |
July 16, 1985 |
Automatic clutch control system
Abstract
A system is provided which controls the pressure with which a
clutch engages, utilizing a slip rate of the clutch which is equal
to the ratio of the rotational speed of the output shaft to the
rotational speed of the drive shaft thereof as a main parameter. A
microprocessor reads a throttle opening and the slip rate at a time
interval of 0.4 sec from the initiation of the clutch engagement,
and accesses a particular group of clutch engagement controlling
data which correspond to the time l elapsed and to these
parameters. The controlling signals of the particular group are
sequentially outputted to the clutch energizing device at a
subinterval of 0.05 sec during the time interval of 0.4 sec. The
interval changes from l=0 to l=8 at maximum, from the initiation to
the completion of the clutch engagement. Each interval l=0 to l=8
corresponds to 0.4 sec. Whenever a temporary clutch activation is
instructed, the microprocessor increases the subinterval of 0.05
sec to 0.1 sec and the time interval l to 0.8 sec. The value of l
is incremented by one after a time length of either 0.4 or 0.8 sec
elapses.
Inventors: |
Oguma; Tomio (Anjyo,
JP), Hirosawa; Kouichiro (Kariya, JP),
Mitsui; Tsutomu (Chiryu, JP) |
Assignee: |
Aisin Seiki Kabushikikaisha
(Kariya, JP)
|
Family
ID: |
12716006 |
Appl.
No.: |
06/357,535 |
Filed: |
March 12, 1982 |
Foreign Application Priority Data
|
|
|
|
|
Mar 27, 1981 [JP] |
|
|
56-45320 |
|
Current U.S.
Class: |
477/87; 192/3.58;
477/119; 701/67 |
Current CPC
Class: |
B60W
10/02 (20130101); B60W 30/1819 (20130101); B60W
30/18 (20130101); F16D 48/066 (20130101); B60W
10/04 (20130101); B60W 10/06 (20130101); F16D
2500/10412 (20130101); F16D 2500/30407 (20130101); F16D
2500/30415 (20130101); F16D 2500/30426 (20130101); F16D
2500/70605 (20130101); F16D 2500/7105 (20130101); F16D
2500/31466 (20130101); F16D 2500/3166 (20130101); Y10T
477/6428 (20150115); Y10T 477/691 (20150115) |
Current International
Class: |
F16D
48/00 (20060101); F16D 48/06 (20060101); B60K
041/28 () |
Field of
Search: |
;192/.052,.075,.076,.092,.096,3.58,13R,.033 ;74/866 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Krizmanich; George H.
Attorney, Agent or Firm: Sughrue, Mion, Zinn, Macpeak, and
Seas
Claims
What we claim is:
1. An automatic clutch control system for a vehicle including a
clutch having a drive shaft and a driven shaft, said system
comprising:
first speed detecting means for detecting the rotational speed of
said drive shaft of said clutch;
second speed detecting means for detecting the rotational speed of
said driven shaft of said clutch;
means for detecting the throttle opening of an engine on said
vehicle;
clutch engagement control means for controlling the degree of
engagement of said clutch in response to clutch engagement control
signals; and
electronic control means connected to said first speed detecting
means, said second speed detecting means, said means for detecting
the throttle opening and said clutch energizing means, and
responsive to the rotational speed of said drive shaft, the
rotational speed of said driven shaft and the throttle opening for
generating and applying a clutch engagement control signal to said
clutch engagement control means, said electronic control means
including memory means for storing a plurality of clutch engagement
control data groups and said electronic control means including
means for specifying, at the initiation of a given time interval, a
particular one of said clutch engagement control data groups in
accordance with a ratio of the rotational speed of the driven shaft
to the rotational speed of the drive shaft and in accordance with
the throttle opening, said electronic control means further
including means for generating a sequence of clutch engagement
control signals corresponding to respective data of the particular
group and for applying said sequence of clutch engagement control
signals to the clutch engagement control means at subintervals
representing a time division of said given time interval.
2. An automatic clutch control system as set forth in claim 1,
wherein the system further comprises means for instructing a
temporary clutch activation control mode, and wherein said
electronic control means increases the duration of said subinterval
when said means for instructing a control mode instructs said
temporary clutch activation control mode.
3. A method of operating an automatic clutch control system in a
vehicle having an engine with a throttle, said system including a
shift lever having a neutral position and at least one run
position, a clutch having drive and driven shafts, first speed
detecting means for detecting the rotational speed of said drive
shaft, second speed detecting means for detecting the rotational
speed of said driven shaft, throttle detecting means for detecting
the opening of a throttle valve, position detecting means for
detecting the position of said shift lever, clutch control means
for controlling a degree of engagement of said clutch in accordance
with a clutch engagement control signal, and electronic control
means for generating said clutch engagement control signal, said
method comprising the steps of:
(a) monitoring said shift lever position for a detected change of
said shift lever position from its neutral position to its run
position;
(b) calculating a ratio of the rotational speed of said driven
shaft to the rotational speed of said drive shaft when said change
in shift lever position is detected and provided that the
rotational speed of the drive shaft is equal to or greater than a
first preset speed value, and applying to said clutch control means
a clutch engagement control signal representing a minimum degree of
engagement of said clutch when said ratio is equal to or less than
a first preset ratio value provided that either the throttle
opening is equal to or greater than a first preset throttle value
or the rotational speed of said drive shaft is equal to or greater
than a second preset speed value;
(c) monitoring said shift lever position and (1) upon detecting
that the shift lever is in its neutral position, applying to said
clutch control means a clutch engagement control signal instructing
the disengagement of said clutch and thereafter returning to said
monitoring step described in paragraph (a) above, and (2) applying
to said clutch control means a clutch engagement control signal
instructing the disengagement of said clutch and returning to said
calculating and applying step described in paragraph (b) above when
said shift lever is in a position other than its neutral position
and said throttle opening is equal to or less than a second preset
throttle value, and when said throttle opening exceeds said second
preset throttle value, effecting a clutch engagement control over a
long time interval by selecting a particular group of clutch
engagement control signals having a level change rate which
corresponds to the current values of said ratio and said throttle
opening and applying to said clutch control means at short time
intervals a sequence of clutch engagement control signals from said
selected group;
(d) effecting clutch engagement control in accordance with the
procedure in the above-described step (c) over successive long time
intervals while continually updating said clutch engagement control
signals until a clutch engagement control signal is applied to said
clutch control means indicating a maximum degree of engagement of
said clutch, and thereafter ceasing the updating of said clutch
engagement control signals, monitoring said shift lever position
and returning to said monitoring step described in paragraph (a)
above if said shift lever is detected in its neutral position, and
monitoring the throttle opening and generating a clutch engagement
control signal indicating disengagement of said clutch and
returning to step (b) above when the throttle opening is equal to
or less than said second preset value;
(e) when said ratio exceeds said first preset ratio value,
comparing said ratio to a second preset ratio value and advancing
to step (c) if said ratio is equal to or less than said second
preset ratio value, and effecting a vehicle braking mode of clutch
control over further long time intervals if said ratio exceeds said
second preset ratio value, said step of effecting a vehicle braking
mode comprising specifying a particular group of clutch engagement
control signals having a signal level change rate which corresponds
to said ratio and applying to said clutch control means at short
time intervals a sequence of clutch engagement control signals from
said specified group while continually updating said clutch
engagement control signals until a clutch engagement control signal
has been applied which indicates a maximum degree of engagement of
said clutch, and thereafter ceasing the updating of said clutch
engagement control signals and monitoring said shift lever
position, the throttle position and the rotational speed of said
drive shaft and returning to step (a) and generating a clutch
engagement control signal for disengaging said clutch if said shift
lever is detected in its neutral position or if the throttle
opening and rotational speed of said drive shaft are not within
given limits.
4. A method according to claim 3, further including the steps of
selecting a temporary clutch activation control mode and, in
response to selection of said temporary clutch activation control
mode, increasing the length of said short time interval at which
said clutch engagement control signals are sequentially supplied to
said clutch control means.
5. A method according to claim 4, further comprising resetting said
control mode to disable said temporary clutch activation control
mode after said vehicle braking mode of clutch control has been
established.
Description
BACKGROUND OF THE INVENTION
The invention relates to an automatic clutch controls system which
automatically control the coupling of a driven shaft to a drive
shaft in a clutch mounted on an automobile in accordance with a
decision rendered by an electronic unit.
In a conventional automatic clutch arrangement, the degree of
engagement of the clutch is determined in an analog manner in
accordance with the number of revolutions of an engine only upon
starting, but an on-and-off control of the clutch is employed
during a subsequent shift operation which occurs after the vehicle
has been started. Consequently, if there is a difference between
the number of revolutions of the engine and the number of
revolutions of the clutch to cause a sudden complete engagement of
the clutch, a driver of the vehicle may experience an uncomfortable
shock. To alleviate this, a variable rate is employed for
engagement of the clutch, since the magnitude of a negative
pressure prevailing in an engine manifold allows the differential
number of revolutions to be known. However, the technique suffers
from a disadvantage that an accurate control cannot be achieved
since the magnitude of the negative pressure changes from vehicle
to vehicle and because a long time delay is involved.
To accomodate for this difficulty, an arrangement has been proposed
to achieve an accurate engagement of a clutch without experiencing
a shock in a clutch arrangement in which a clutch transmits
rotating power to an output shaft. The arrangement comprises a
power sensor for detecting the number of revolutions of the output
shaft, a clutch sensor for detecting the number of revolutions of
the clutch, a comparator for determining the relative magnitude of
the number of revolutions of both sensors, a parameter of follow-up
control responsive to an output from the comparator to activate the
clutch for engagement as the number of revolutions of the output
shaft increases whenever the number of revolutions of the output
shaft is higher than that of the clutch, and an automatic engaging
circuit responsive to an output from the comparator and operating
whenever the number of revolutions of the clutch is higher to
deactuate the follow-up control and to terminate automatically the
engagement of the clutch within a given time interval. In this
manner, the relative magnitude of the number of revolutions of the
engine and the clutch is determined in an electrical manner, and
whenever the number of revolutions of the engine is higher than
that of the clutch, an engagement of the clutch occurs in response
to the number of revolutions of the engine while whenever the
number of revolutions of the engine is lower than that of the
clutch, an engagement of the clutch takes place in accordance with
a difference therebetween. (See Japanese Patent Publication No.
26,020/1978, filed Mar. 26, 1971 and published July 31, 1978). In
other words, the rotational speed of the engine is chosen as a main
variable while a differential speed between the output shaft of the
clutch (driven shaft) and the output shaft of the engine (the
clutch drive shaft) is chosen as a parameter for controlling the
clutch coupling power. To summarize, in a mode in which the vehicle
is driven for running under the engine power, the clutch coupling
power is controlled in a manner corresponding to the rotational
speed of the engine while in an engine brake mode, the clutch
coupling power is controlled as a particular function of time.
Consequently, the slip rate of the clutch depends on the rotational
speed of the engine, and the correlation between the engine power
and a load on the vehicle may not be proper. To achieve a proper
engagement of a clutch for various running conditions of a vehicle,
it is preferred that the slip rate of the clutch correspond to the
running condition of the vehicle.
SUMMARY OF THE INVENTION
It is a first object of the invention to provide an automatic
clutch control system which controls the engagement of a clutch in
accordance with the slip rate of the clutch and as a function of
the running condition of a vehicle. A second object is to provide
an automatic clutch control system which controls the clutch
engagement in accordance with an engine power and a loading on the
vehicle, and a third object is to provide an automatic clutch
control system which enables a smooth and proper clutch engagement
in accordance with the running condition of a vehicle and the
engine power.
The above objects are accomplished in accordance with the invention
by controlling the clutch engagement as a function of an actual
slip rate of the clutch, namely, the ratio of the rotational speed
of the drive shaft to the rotational speed of the driven shaft of
the clutch. Specifically, a target slip rate is determined as a
function of an actual slip rate, and the actual slip rate is
determined at a given time interval to derive the corresponding
target slip rate, and a clutch controlling signal is applied to
clutch controlling and energizing means which is capable of
achieving the specified target slip rate.
In a preferred manner of carrying out the present invention, a
throttle opening which can be related to an engine power is
utilized to change the correlation between the target slip rate and
the actual slip rate. Thus, the actual slip rate and the throttle
opening are detected at a given time interval, and both of them are
used to specify a particular target slip rate. A clutch controlling
signal is applied to the clutch controlling and energizing means
which is capable of achieving the specified target slip rate.
It will be seen that the combinations of the engine power (throttle
opening) and the actual slip rate are innumerable because both of
them are analog in nature. To enable an electronic control, both of
them must be quantized to assume values in a plurality of zones.
Nevertheless, there are an increased number of combinations of the
throttle opening and the actual slip rate. It is preferred that the
slip rate be changed at a rate dependent on the correlation between
the engine power and a running condition of the vehicle so that the
rate is low when the engine power is low and the loading on the
vehicle is high while the rate is high when the engine power is
high and the loading on the vehicle is low. Accordingly, in a
preferred embodiment of the invention, the clutch controlling
signal which is specified at a given time interval comprises a
group or a set of clutch controlling signals which are specified
during subintervals which represent a time division of the time
interval. When a particular group of controlling signals is
specified, the controlling signals belonging to the particular
group are sequentially addressed at the time subinterval for
application to the clutch controlling and energizing means. In this
manner, a proper rate of change of the slip rate is determined at
the given time interval as a function of the actual slip rate or
the actual slip rate and the throttle opening. It will be seen that
the actual slip rate at a given time and the number of times the
given time interval has been repeated, or the clutch controlling
signal has been changed by that time, correspond to the prevailing
value of the engine power and the loading on the vehicle. It then
follows that a particular group of clutch controlling signals which
is specified next has a rate of change of the slip rate which is
proper to these parameters. In this manner, by changing the group
of clutch controlling signals at a given time interval, a smooth
control of the clutch engagement is achieved. As the number of
times the groups of clutch controlling signals are changed
increases, or as the time passes since the initiation of
controlling the clutch engagement, the actual slip rate
successively increases, and accordingly, the target slip rate also
increases in a sequential manner. Thus, a reduced number of groups
of clutch controlling signals may be used. Therefore, if a
particular group of clutch controlling signals is specified in
terms of the actual slip rate and the throttle opening, the
required number of groups of controlling signals is far less than
the number of zones of the slip rate, multiplied by the number of
zones of a throttle opening and the number of controlling signals
is changed.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block diagram of an embodiment of the invention,
illustrating essential components used therein in combination with
a vehicle;
FIG. 2 is a block diagram showing the general arrangement of the
embodiment in more detail;
FIGS. 3a, 3b, 3c, 3d and 3e are circuit diagrams showing the detail
of individual components shown in block form in FIG. 2;
FIG. 4 graphically shows clutch controlling data which is stored in
read only memories shown in FIGS. 1 and 2;
FIGS. 5a, 5b, 5c and 5d graphically show part of the data
illustrated in FIG. 4 representing the data used to control
starting on a flat road, starting on an up slope, starting on a
very steep up slope and to control engine braking,
respectively;
FIGS. 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h and 6i are flowcharts
illustrating a clutch control operation by a central processing
unit shown in FIG. 2 based upon program data stored in the read
only memories also shown in FIG. 2;
FIGS. 7a, 7b and 7c graphically show a change in the rotational
speed Ne of the engine when starting on a flat road, on an up slope
and on a very steep up slope, respectively;
FIG. 7d graphically shows a change in the rotational speed No of
the driven shaft of the clutch during an engine brake control;
FIGS. 8a and 8b graphically show a clutch turn-on characteristic in
response to a change in the vehicle loading and the throttle
opening during a temporary clutch activation;
FIG. 8c graphically shows regions where the engine brake can be
applied and cannot be applied;
FIG. 8d graphically shows the clutch turn-on response during a
manual temporary clutch activation;
FIG. 8e graphically shows the clutch on-off region in relation to
the throttle opening and the rotational speed of the engine.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring to the drawings, an embodiment of the invention will now
be described. FIG. 1 is a block diagram illustrating the general
arrangement of an embodiment of the invention, principally
illustrating its relationship with an engine and a clutch mounted
on a vehicle. Specifically, an engine 10 includes a throttle valve
11 having a rotary shaft, to which a throttle opening sensor 12 is
coupled. A rotation sensor 20 is coupled to the drive shaft of a
clutch 30, which represents the output shaft of the engine while
another rotation sensor 40 is coupled to the driven shaft of the
clutch. The clutch 30 shown comprises a wet multi-disc clutch as
disclosed in U.S. Pat. Nos. 2,738,864 and 4,242,924, for example.
The clutch includes a piston, to which an oil pressure is applied
depending on the operative condition of a solenoid operated
pressure regulator valve 60 and a switch valve 50. It is to be
understood that the switch valve 50 may be omitted while using a
pressure regulator valve 60 which can be controlled to its fully
closed position. It is to be noted here that the clutch 30 may also
be replaced by a solenoid operated clutch as disclosed in U.S. Pat.
Nos. 2,774,452 and 3,249,184, for example, with the valves 50, 60
replaced by solenoid drivers. As a further alternative, any other
clutch which can be electrically controlled may be used.
A shift lever which establishes a particular operational mode of a
transmission is associated with a position sensor 13 which
determines the established position thereof.
A detection signal from the throttle opening sensor 12, detection
signals from the rotation sensors 20 and 40, and a position signal
from the sensor 13 are fed to an interface (electrical processing
circuit) 70 where they are amplified, waveform shaped and converted
into digital versions to be applied to a microprocessor system 90.
It will be noted that the interface 70 is also connected to a
manual switch 14 which instructs a temporary clutch activation as
when the traffic on the road is congested. Its status signal is
applied to the microprocessor system 90.
The microprocessor system 90 includes a semiconductor read only
memory (ROM or PROM) storing groups of clutch controlling signals.
It reads the number of revolutions Ne of the clutch drive shaft,
the number of revolutions No of the driven shaft, the throttle
opening T.theta., the shift lever position Sp and the like in order
to access the memory to read out clutch controlling data, which is
supplied to the interface 70 to control the pressure regulator
valve 60.
FIG. 2 shows the general arrangement of one embodiment of the
invention while FIGS. 3a to 3e show the details of various parts.
First, referring to FIGS. 2 and 3a, a system for detecting the
rotational speed of the drive shaft of the clutch will be
described. The clutch drive shaft fixedly carries a permanent
magnet gear having a plurality of teeth formed along its periphery,
with adjacent teeth being magnetized to opposite polarities. A core
of a magnetizable material is disposed in opposing relation with
the teeth and carries a sensor coil thereon, the assembly forming
the rotation sensor 20. As the magnet gear rotates, an alternating
voltage is induced in the sensor coil, and is applied to amplifier
and waveform shaper circuit 72 of the interface 70. The circuit 72
includes a first operational amplifier OP1 which inverts and
amplifies the input alternating voltage, a second operational
amplifier OP2 which again inverts, amplifies it and shifts its
level, and a first and a second transistor which convert the input
into a binary signal, which is then inverted and amplified. As a
result of such arrangement, there are produced speed detection
pulses of a frequency and a pulse width which depend on the
rotational speed of the magnet gear 20, and which are applied to a
monostable multivibrator MM1. The monostable multivibrator MM1 is
triggered by the rising end of the speed detection pulse to produce
a pulse output of high level or "1" which has a given short
duration. In this manner, the output from the monostable
multivibrator MM1 represents a sequence of pulses of a given pulse
width and having a frequency which is proportional to the
rotational speed of the clutch drive shaft and which is indicative
of the engine speed. The sequence of pulses are passed through NAND
gate NA1 to be applied to a counter latch 74 of the interface 70,
which comprises a pair of four bit counters CO1, CO2, and latch
LA1. The sequence of pulses are counted by the counter CO1, and a
carry pulse from the counter CO1 is counted by the counter CO2. In
this manner, the combination of the counters CO1 and CO2 forms an 8
bit counter. The count in the counters CO1 and CO2 are used to
update the content of the latch LA1 at a given time interval,
whereupon the counters CO1, CO2 are cleared. Therefore, data stored
in the latch LA1 represents a number of engine speed detection
pulses obtained during a given period, or the rotational speed of
the engine. A timer 73 controls the updating operation of the latch
LA1 and the clearing operation of the counters CO1, CO2. In the
timer 73, pulses produced by a pulse oscillator OSC are frequency
divided by a combination of a counter CO3 and NAND gates NA2 and
NA3 to form a latching instruction pulse and a counter clear pulse.
The counter clear pulse is converted into a pulse of a reduced
width by means of a monostable multivibrator MM2 to clear the
content of the counters CO1, CO2 momentarily subsequent to
activating or updating the latch LA1.
Referring to FIGS. 2 and 3b, a system for detecting the rotational
speed of the driven shaft of the clutch as well as a system for
detecting the direction of rotation of the driven shaft of the
clutch will now be described. The driven shaft of the clutch
includes a permanent magnet gear which is similar to that provided
in the rotation sensor 20, and also includes a pair of cores 41, 42
of a magnetizable material each carrying a detection coil thereon
and which are disposed in opposing relationship with the gear. The
cores are disposed so that voltages induced in the respective
detection coils have a phase difference of .pi./2 therebetween.
These induced voltages are applied to amplifier and waveform shaper
circuits 75, 76, respectively. The circuit 75 is arranged in the
same manner as the circuit 72 mentioned before while the circuit 76
is similar to the circuit 72, except that the monostable
multivibrator MM1 is omitted therefrom. The output pulses from the
circuit 75, representing the rotational speed of the driven shaft
of the clutch, are applied to a counter and latch circuit 77, which
is constructed in the same manner as the counter and latch circuit
74. As before, the circuit 77 receives a latching instruction pulse
and a counter clear pulse which are the same as those applied from
the timer 73 to the circuit 74. In this manner, data stored in the
latch represents the rotational speed of the driven shaft of the
clutch. Pulses Nop1, Nop2 from the circuits 75, 76 have a phase
difference of .pi./2 therebetween, and are applied to a direction
discriminating element FF2 of a direction of rotation
discriminating circuit 78. Specifically, the element FF2 is formed
by a J-K flipflop, and produces a low level or "0" output when the
driven shaft rotates in a direction corresponding to the forward
direction of the vehicle and produces a high level or "1" output
when the driven shaft rotates in a direction corresponding to the
reverse direction of the vehicle, in accordance with a phase
difference between the pulses Nop1, Nop2.
FIG. 3c shows the general construction of the throttle opening
sensor 12 and a processing circuit 71, representing a part of the
interface 70, which processes a detection signal from the sensor
12. The throttle opening sensor 12 includes a printed substrate on
which five electrodes 12a.sub.1 -12a.sub.5 are formed. The sensor
12 includes a rotary shaft connected electrically to the ground and
also connected to the rotary shaft of the throttle valve and
fixedly carrying a slider electrode having five radially extending
brush arms 12b.sub.1 -12b.sub.5. A rotation of the throttle valve
corresponding to an opening from 0% to 100% is limited within
360.degree./5, and accordingly, the brush arms 12b.sub.1 -12b.sub.5
are angularly spaced apart from each other by 360.degree./5. A
first electrode 12a.sub.1 has a width which enables its contact
with a first arm 12b.sub.1 to be maintained as the opening lies
within an extent less than 0% to 5%. A second electrode 12a.sub.2
has a width which enables its contact with a second arm 12b.sub.2
to be maintained for an opening within an extent from less than 5%
to 35%. A third electrode 12a.sub.3 has a width which enables its
contact with a third arm 12b.sub.3 to be maintained for an opening
within an extent from less than 35% to 60%, a fourth electrode
12a.sub.4 has a width which enables its contact with a fourth arm
12b.sub.4 to be maintained for an opening within an extent from
less than 60% to 80%, and a fifth electrode 12a.sub.5 has a width
which enables its contact with a fifth arm 12b.sub.5 to be
maintained for an opening within an extent from less than 80% to or
above 100%. To avoid a condition that none of the arms 12b.sub.1
-12b.sub.5 contacts either electrode 12a.sub.1 -12a.sub.5, an
arrangement is made so that arms 12b.sub.1 and 12b.sub.2 contact
the electrodes 12a.sub.1 and 12a.sub.2, respectively, at an opening
of 5% including a slightly lesser opening, the arms 12b.sub.2 and
12b.sub.3 contact the electrodes 12a.sub.2 and 12a.sub.3,
respectively, at an opening of 35% including a slightly lesser
opening, the arms 12b.sub.3 and 12b.sub.4 contact the electrodes
12a.sub.3 and 12a.sub.4, respectively, for an opening of 60%
including a slightly lesser opening, and the arms 12b.sub.4 and
12b.sub.5 contact the electrodes 12a.sub.4 and 12a.sub.5,
respectively, for an opening of 80% including a slightly lesser
opening. As a consequence, two electrodes may assume a ground level
simultaneously. To enable an opening detection signal to be
uniquely defined under such condition, the processing circuit 71 is
arranged such that the potential assumed by the electrodes
12a.sub.1 -12a.sub.5 is applied, after amplification, to OR gates
OR2-OR5 both directly and through inverters IN1-IN4 so that a
detection signal corresponding to a lower opening is initially
outputted. Table 1 below indicates a throttle opening detection
code corresponding to a particular value of throttle opening
T.theta. (%).
TABLE 1 ______________________________________ throttle valve
opening T.theta. code T.theta. (%) I.sub.17 I.sub.18 I.sub.19
I.sub.20 I.sub.21 ______________________________________ T.theta.
.ltoreq. 5 1 1 1 1 0 5 < T.theta. .ltoreq. 35 1 1 1 0 1 35 <
T.theta. .ltoreq. 60 1 1 0 1 1 60 < T.theta. .ltoreq. 80 1 0 1 1
1 80 < T.theta. 0 1 1 1 1 ______________________________________
Note: "0" represents a low level and "1" a high level.
Referring to FIG. 3d, a system for detection of the position of the
shift lever will be described. The shift lever position sensor 13
comprises a switch 13.sub.1 which is closed at the neutral position
N, and another switch 13.sub.2 which is closed at the reverse
position R. These switches are connected to an amplifier 79 of the
interface 70. The manual switch 14 which is used to prolong the
temporary clutch activation is connected to a flipflop FF1. The
relationship between the opening and the closing of these switches
and the status code is indicated in Table 2 below. It is to be
noted that the flipflop FF1 is set in response to the closure of
the switch 14 and is reset by the microprocessor unit 90.
TABLE 2 ______________________________________ shift lever switches
Sp code position 13.sub.1 13.sub.2 14 I.sub.22 I.sub.23 I.sub.24
I.sub.25 ______________________________________ neutral N closed x
x 0 1 1 1 drive D x x x 1 0 1 1 reverse R x closed x 1 1 0 1 manual
set x x momentarily 1 1 1 0 closed
______________________________________ Note: "0" represents a low
level while "1" a high level, and the mark "x" represents an open
condition.
The remainder of the interface 70, namely, a solenoid driver 80
which controls the energization of the switch valve 50, a D/A
converter 81 and another solenoid driver 82 which controls the
energization of the pressure regulating valve 60 will now be
described with reference to FIG. 3d. The microprocessor unit 90
produces a clutch control signal on its output ports O.sub.0
-O.sub.12 where it is latched. The signal appearing on the port
O.sub.0 represents a controls signal which control the opening or
closing of the switch valve 50; the signal appearing on the port
O.sub.1 represents a reset control signal for the flipflop FF1; and
signals appearing on other ports O.sub.2 -O.sub.12 represent
control signals for the pressure regulating valve or data
controlling the energization of the clutch. In the solenoid driver
80, the valve control signal O.sub.0 is applied to a monostable
multivibrator MM3 and also to NAND gate NA4, which also receives a
timing pulse D from the timer 73 (FIG. 3a) and Q output from the
monostable multivibrator MM3. When the signal O.sub.0 assumes a
high level or "1" indicating that the valve 50 is to be opened, the
Q output of the monostable multivibrator MM3 remains at its low
level or "0" during a subsequent period which is preset with this
multivibrator, whereby the output from NAND gate NA4 continuously
assumes a high level or "1", thus maintaining a transistor Tr3 off.
At this time, both transistors Tr4 and Tr5 conduct to permit a
solenoid associated with the valve 50 to be continuously energized.
Consequently, the plunger of the valve 50 is strongly driven in a
direction to open the valve, thus opening the valve 50. When the Q
output from the monostable multivibrator MM3 returns to its high
level or "1" after the given period, the output from the gate NA4
varies between its high and low levels in accordance with the
timing pulse D. It is to be noted that the level variation has a
duty cycle of 50%. In this manner, the transistor Tr5 is repeatedly
turned on and off in synchronized relationship with the level
variation of the timing pulse D, whereby the current flow through
the solenoid of the valve 50 as average over the time is reduced to
one-half its previous value. However, because the plunger of the
valve 50 has moved to its open position and is maintained in
contact with the attracting yoke, it remains in its valve open
position. In other words, the level of energization of the solenoid
is increased during the initial phase of driving the plunger so as
to provide an increased magnitude of drive force while the
energization level is reduced to suppress the heating of the
solenoid after the valve has been driven to its open condition. The
solenoid driver 82 receives an analog energization signal from the
D/A converter 81, as instructed by the clutch control code
(hereafter referred to as Cp code). A transistor Tr6 controls the
conduction of another transistor Tr7 in accordance with the level
of the analog signal. Accordingly, there occurs a current flow
through a solenoid associated with the pressure regulating valve
60, of a level as instructed by the Cp code. The plunger of the
valve 60 having a throttle opening remains at the position which
corresponds to the energization level of the solenoid.
FIG. 3d also shows a power supply unit 110. As shown, a main
battery mounted on the vehicle supplies a d.c. voltage of 12 V,
which is stepped down to and maintained at a constant value of 5 V
by means of a constant voltage element 111. This voltage is then
stepped up to a value of 30 V by a DC/DC converter 112, which has a
center tap, located at a voltage level of 15 V, which is connected
to the ground, thus supplying .+-.15 V to the D/A converter 81.
FIG. 3e shows the general arrangement of the microprocessor unit
90. The unit 90 comprises a microprocessor 91 (hereafter referred
to as CPU), a pair of semiconductor read only memories 92, 93
(hereafter referred to as ROM1 and ROM2) having input/output ports,
and a semiconductor read-write memory 94 (hereafter referred to as
RAM) having input/output ports. The unit includes a reset circuit
100 to which a voltage of 5 V is supplied. Immediately after the
application of the voltage 5 V and thereafter whenever a reset
switch 101 is closed, the reset circuit produces a reset signal
which is applied to CPU 91. In response to the reset signal, CPU 91
effects an initialization of its input/output ports.
Principal components described above are formed by IC elements,
which are specified in Table 3 below.
TABLE 3 ______________________________________ reference produce
components character manufacturer number
______________________________________ counter CO1, CO2 Motorola
MC14029B counter CO3 " MC14518B latch LA1 " MC14508B monostable
MM1, MM2 " MC14027B multivibrator monostable MM3 " MC14528B
multivibrator direction FF2 " MC14027B discriminating element CPU
91 Intel 8085 ROM 92, 93 " 8755 RAM 94 " 8156
______________________________________
Clutch controlling programs and data for controlling the
energization of the clutch are previously stored in ROM 92, 93 of
the microprocessor unit 90. Data controlling the energization of
the clutch will be generally described first. The clutch
energization controlling data is divided into segments each having
a length of 0.4 sec (l=0 to l=8), each of which is assigned with
one group or several groups of clutch energization controlling
data. In FIG. 4, the segment l=0 has an assignment of ten groups,
the segment l=1 has an assignment of fifteen groups, . . . and the
segment l=8 has an assignment of a group of clutch energization
controlling data. While clutch energization controlling data of
each group is shown to assume a continuous value with time t in
FIG. 4, it is to be understood that as indicated by dots for the
segment l=0 in FIG. 5a, the interval of 0.4 second is subdivided
into eight equal divisions or subintervals each having a length of
0.05 sec. In other words, a single group in each segment (l)
includes eight clutch energization controlling data, each of which
is read as a time length of 0.05 sec passes. Such clutch
energization controlling data is stored in ROM 92 and 93, and a
particular group is specified by i=1 to 9, j=1 to 4 and l=0 to 8.
K=1 to 8 specifies a particular controlling data within a given
group, corresponding to a point on a curve shown in FIGS. 4 and 5a.
Upon starting the vehicle, l=0 is chosen, and 1 is incrementally
added to increase the magnitude of l after each 0.4 sec interval.
Thus, l indicates the lapse of a time interval of 0.4 sec while K
is incremented by one for each time length of 0.05 second during a
particular value of l, with K=9 returning to K=1. Thus, K indicates
the elapse of a subdivision time. The character "i" indicates a
load on the vehicle, and upon starting the vehicle (l=0), the load
on the vehicle is determined on the basis of a rate of change of
the rotational speed of the engine, dNe/dt, when the clutch has
just been engaged and the value of i is determined in accordance
with the magnitude of the load. However, during l=1 and subsequent
segments, the value of i is determined in accordance with the
actual slip rate e=No/Ne. The character "j" indicates an engine
power, which is determined on the basis of the throttle opening
T.theta.. Thus, from the starting of the vehicle until the clutch
is completely engaged, a combination of the 0.4 sec segment l, the
load on the vehicle i and the engine power j determines a
particular group of clutch energization controlling data, each
including eight data which define the rate of level change (the
rate of engagement of the clutch e/dt; t is represented in terms of
K units or 0.05 sec) for the particular group. In each segment
shown in FIG. 4, where a curve is branched, the branch is
determined by i and j. In FIG. 4, a hatched region represents an
extent where a clutch slip rate e does not exist actually upon
starting the vehicle. No clutch controlling data is necessary in
such region, and hence no corresponding data is stored in ROM 92
and 93. To prevent such region from being inadvertently accessed, a
data access program, to be described later, prevents an address
within the hatched area in FIG. 4 from being specified.
Accordingly, clutch controlling data stored in the ROM 92, 93 is
determined by an address having l=0 to 8, i=1 to 9, j=1 to 4 and
K=1 to 8 as parameters. Though the number of the parameters is
increased, the number of data is not so much.
Considering the clutch controlling data shown in FIG. 4, they
include data which are utilized for the purpose of control when
starting upon a flat road, upon starting on an up slope, when
starting upon a very steep slope, when starting on a down slope,
and when applying an engine brake.
FIG. 5a illustrates several data which may be used when starting on
a flat road. As indicated in FIG. 5a, the clutch energization
controlling data Vs (a voltage controlling the pressure regulating
valve 60) has a reduced magnitude of change rate (dVs/dt) whenever
the throttle opening T.theta. or j is small, but has a greater
change rate if the throttle opening T.theta. has a greater value.
FIG. 5b illustrates several data which may be used upon starting on
an up slope. When running on an up slope, the load imposed upon the
vehicle is high, so that the change rate dVs/dt is established at a
lower value. FIG. 5c illustrates data utilized when starting on a
very steep up slope. In this instance, the load applied to the
vehicle is further increased, so that a greatest length of time is
established for the slip rate e to change from 0 to 1. Accordingly,
the change rate dVs/dt assumes the smallest value. FIG. 5d
illustrates data used when starting on a down slope and when
applying an engine brake. When starting on a down slope or applying
an engine brake, the vehicle drives the engine and hence a greater
value is used for the change rate dVs/dt.
ROM 92, 93 store a clutch control program which is used to control
the clutch, in addition to the clutch energization controlling data
mentioned above.
FIGS. 6a to 6i are flowcharts illustrating clutch control
operations performed by the CPU 91 in accordance with the program
stored. Referring to these Figures, the operation of the
microprocessor unit 90 will be described in detail below.
(1) Decision of load on the vehicle upon initiating a clutch
control, and the clutch control during the first segment l=0:
When the power is turned on, CPU 91 effects an initialization of
its input/output ports I.sub.0 to I.sub.26 and O.sub.0 to O.sub.12,
and produces a low level or "0" on the output port O.sub.0
connected to the switch valve 50, indicating the closure of the
valve. A clutch controlling data Vs1 is produced on the output
ports O.sub.2 to O.sub.12 connected to the pressure regulating
valve 60 which would establish a very low oil pressure insufficient
to cause an engagement of the clutch or which maintains the slip
rate e of the clutch substantially zero. The shift lever position
(Sp code) is then read, and if it indicates the neutral position N,
the unit remains in its standby mode. If the shift lever position
is either drive D or reverse R position, the CPU applies a high
level or "1" to the output port O.sub.0, causing the valve 50 to be
opened. In response thereto, an oil pressure which substantially
corresponds to e=0 is applied to the clutch 30. The CPU 91 then
reads the rotational speed of the engine (Ne code), and if the
engine speed Ne is less than 900 rpm indicating an idling condition
and the absence of an energization for starting or the depression
of an accelerator pedal, it waits for the energization for starting
or an engine speed equal to or greater than 900 rpm, or the
depression of the accelerator pedal. When an engine speed equal to
or greater than 900 rpm is reached, the rotational speed of the
driven shaft of the clutch (No code) is read to calculate the
actual slip rate e. At this stage, e.congruent.0 unless the vehicle
is running on a down slope, and e.gtoreq.0 if the vehicle is
running on a down slope. The above operation is illustrated by the
flowchart shown in FIG. 6a. When the vehicle is substantially at
rest (e.ltoreq.0.1.fwdarw.YES), the CPU jumps to the flowchart
shown in FIGS. 6b to 6d where the load on the vehicle is detected.
In this flowchart, the CPU 91 initially reads the throttle opening
(T.theta. code), and if the throttle opening T.theta. is less than
60%, indicating a setting for the engine power which is relatively
low, it refers to the engine speed Ne to determine if it is equal
to or greater than 1200 rpm which enables a starting operation. If
the engine speed is less than 1200 rpm, the starting operation is
disabled, and hence it waits for the throttle opening to reach or
exceed 60% or for the engine speed to reach or exceed 1200 rpm. In
response to T.theta..gtoreq.60% or Ne.gtoreq.1200 rpm, the CPU 91
reads the rotational speed of the driven shaft of the clutch (No
code) and if it indicates zero, produces a given controlling data
Vs2 on the output ports O.sub.2 to O.sub.12 connected to the
pressure regulator valve 60 which establishes a slip rate e
slightly greater than zero. It then reads the rotational speed of
the engine Ne at an interval of 0.05 sec, and makes a decision to
see if Ne-Ne1.ltoreq.0, by comparing the current value of Ne with a
value Ne1 which has been read 0.05 sec earlier. In other words, it
waits for a reduction in the engine speed Ne in response to the
application of the signal Vs2. If a reduction in the engine speed
Ne occurs, it determines that a slight engagement of the clutch has
occurred or the engagement of the clutch has been initiated. The
CPU then stores the prevailing Ne code in a register Ne1 or updates
the engine speed, and clears a number of times register l. After
0.1 second, it reads the Ne code again in order to calculate the
change rate of the engine speed dNe/dt=Ne1-Ne. The rate dNe/dt has
an increased value when the load on the vehicle is high (or when
the weight of the vehicle is high and when running on a up slope),
and has a low value when the load is low. Count 1 is entered into a
register K which specifies a particular subinterval address to
provide a clutch control during the first segment l=0 (where l
represents the content of a register l), thus specifying the first
data of this segment. Also, a load representing code i (which
represents the content of a register i) is loaded into the register
i in accordance with the load on the vehicle dNe/dt previously
calculated. The described operation is illustrated by the
flowcharts shown in FIGS. 6b and 6c.
The relationship between the timing of determining the load and the
behaviour of the engine speed Ne is illustrated in FIGS. 7a, 7b and
7c. FIG. 7a illustrates the relationship when starting on a flat
road, FIG. 7b when starting on an up slope and FIG. 7c when
starting on a very steep up slope. FIG. 7d graphically shows a
change in the speed of the driven shaft of the clutch during an
engine brake mode, to be described later, when the vehicle is
running.
Referring to the flowchart shown in FIG. 6d, the CPU 91 reads
T.theta. code, and stores an engine power representing code j
(which represents the content of a register j) into the register j
in accordance with the T.theta. code or the engine power. At this
point in time, it will be seen that a code specifying the first
segment l=0 is stored in the register l, a code specifying the
first data K=1 is stored in the register K, a code representing the
vehicle load i is stored in the register i, and a code representing
the engine power j is stored in the register j, respectively. This
point in time corresponds to the origin of the curves shown in
FIGS. 4, 5a, 5b, 5c and 5d. The CPU 91 then reads out data from the
registers i, j, K and l to make up an address to read out a first
clutch controlling data (K=1) of a particular group specified by
the values of i and j from either ROM 92 or 93, it being recalled
that a single group includes eight clutch energization controlling
data. The data read out is stored in an output register Cp, and is
also outputted on the output ports O.sub.2 to O.sub.12. As a
result, a clutch control voltage Vs3 (l=0, K=1) which follows the
voltage Vs2 is applied to the D/A converter 81 and thence to the
solenoid driver 82. Consequently, the energization level of the
solenoid associated with the pressure regulating valve 60 is
increased so as to correspond to the magnitude of Vs3, and the
opening of the valve 60 also increases, thus increasing the
pressure with which the clutch 30 is engaged and also increasing
the slip rate e. When a time interval of 0.05 sec passes
subsequently, the CPU 91 then increments the content of the
register K by one to access either ROM 92 or 93 in terms of the
parameters i, j, K and l, thus reading out a next following clutch
controlling data Vsx. The data read out is stored in the register
Cp and is also outputted on the output ports O.sub.2 to O.sub.12.
When the content of the register K reaches 9, the content of the
register l is changed to l=1. This completes the clutch control for
the first segment l=0. In the described control for the first
segment l=0, it should be noted that the values of i, j and l are
not updated when making a successive read-out (K=1 to 8) of data
from ROM. It is also to be noted that the detection of the vehicle
load takes place together with the detection of a downward reversal
of the engine speed as well as the calculation of dNe/dt.
(2) A selection of clutch control mode and resetting after the
initiation of clutch control:
When the number of times register l is set to 1, the CPU 91 reads
the shift lever position (Sp code), and if it has changed to the
neutral N position, it returns to waiting for the starting
illustrated in FIG. 6a, inclusive of a waiting for a change from
the neutral N position to the drive D or reverse R position during
the running. If the shift lever position remains to be the drive D
or reverse R position, the CPU 91 reads the throttle opening
T.theta. and if it indicates an opening (corresponding to a value
less than 6% and the release of the accelerator pedal) which
indicates an idling condition, it determines that a starting stop,
inclusive of a vehicle stop and an engine braking, is instructed,
thus returning to reading the shift lever position as indicated in
FIG. 6a. If the throttle opening T.theta. is equal to or greater
than 6%, indicating a forward advance, the CPU 91 then resets the
register K to K=1, and calculates the slip rate e by reading the Ne
code and No code. The slip rate e which prevails corresponds to the
load on the vehicle, and hence the value of i is determined in
accordance with the value of e and stored in the register i. In the
second segment l=1, a preset value of the slip rate is above 0.2 as
shown in FIG. 4, and thus any slip rate exceeding 0.2 is subject to
the decision. However, during the segments which are equal to or
greater than l=2, the value of the slip rate e which is to be
determined is limited to its higher side as shown in FIG. 4, the
lower limit of the slip rate which is to be determined being
sequantially shifted toward the higher side (refer to the flowchart
in the lower half of FIG. 6e and FIG. 6f). Considering the
flowchart for the second segment l=1, CPU 91 then reads the
throttle opening (T.theta. code), and determines the value of i in
accordance with the throttle opening to be stored in the register
i. It then proceeds through the decision "I.sub.25 ="1"?" to see if
the temporary clutch activation prevails for reason of the
congested road condition, to be described later, and if the
temporary clutch activation is defective, it establishes a longer
value 0.1 sec for the sampling time tt during which the value of K
is to be updated, and it establishes a standard value of 0.05 sec
if the temporary clutch activation is not effective. Then it reads
ROM 92 or 93 at an address defined by the content of the registers
i, j, K and l to derive a clutch controlling code Vsx, which is
then stored in the output register Cp and is also outputted on the
output ports O.sub.2 to O.sub.12. After the time limit of tt, the
value of K is changed from K=1 to K= 2. It then similarly reads
data from ROM, and increments the value of K for each time limit of
tt. When K=9 is reached, the content of the register l is
incremented by one, thus returning to reading the shift lever
position as shown in FIG. 6d. The described operation is
illustrated by the flowchart extending from the lower portion of
FIG. 6d to FIG. 6g. As mentioned previously, each group of clutch
energization controlling data includes eight clutch control data in
principle, each of which is defined by K=1 to 8. However, after
reading clutch control data Vsm corresponding to e=1 and applying
it on the output ports, the clutch 30 is reset to the slip rate
e=1. Hence, a clutch on control from its non-engaged condition to
its perfect engagement has been completed. Accordingly, before the
step of reading data from ROM illustrated in FIG. 6f, the content
of the output register Cp is compared against the code Vsm which
establishes e=1, and if it is found that the content of the output
register Cp is equal to Vsm, data reading from ROM is skipped. This
means that when Vsm appears in a particular group of data at a
point where K=1, i<8, data for K=i+1 and greater are omitted.
Accordingly, after the output supplied to the pressure regulating
valve 60 reaches Vsm, this output is maintained. When the throttle
opening subsequently changes to an idling opening (engine brake),
the arrangement returns to the detection of the shift lever
position illustrated in FIG. 6a from the third step illustrated in
FIG. 6e. When the shift lever position changes to the neutral N
position, the flowchart returns from the first step of FIG. 6e to
the clutch non-engaged step of FIG. 6a. As long as the shift lever
position remains in its drive D or reverse R position with
T.theta..gtoreq.6%, the clutch controlling code Vsm indicating e=1
continues to be applied to the output ports O.sub.2 to
O.sub.12.
To summarize, the shift lever position Sp, the load on the vehicle
i and the engine power j are read at an interval of 0.4 sec (when
tt=0.05 sec or at an interval of 0.8 sec for tt=0.1 sec), and in
response to each reading, a clutch control is performed in
accordance with the established value or condition. The data group
is selected in terms of i, j and the elapsed time l at an interval
of 0.4 sec until e=1 (Vsm) is reached, and within the interval of
0.4 sec, clutch controlling data Vsx within the particular group is
changed at a short time interval or subinterval of 0.05 sec.
Accordingly, the control of the clutch engagement starts with e=0,
and is completed with e=1. During this process, any change in the
vehicle load i or the engine power j causes the rate of change in
the engagement of the clutch (de/dt or dVs/dt) to be changed
accordingly, thus assuring a proper clutch control in accordance
with both the road condition and the operation of the accelerator
pedal by the driver.
Considering this in more detail, assuming a throttle opening of 50%
and that the vehicle is running on an up slope having an
inclination .alpha.=14.degree. at the origin or the start of the
clutch control as indicated in FIG. 8a, the throttle opening is
increased to 100% until the end of l=1. When .alpha.=0.degree., a
particular group of data is specified by the opening of 100% and
the prevailing slip rate e corresponding to .alpha.=0.degree.
during the next segment l=1, thus establishing an increased value
for dVs/dt to accelerate the clutch engagement (e=1). When the
reverse is true, a smaller value is established for dVs/dt to
retard the clutch engagement (e=1) with a reduction in the throttle
opening and an increase in the vehicle load, as indicated in FIG.
8b.
(3) Clutch control when starting on a down slope and when applying
an engine brake:
When starting on a down slope, if the slope has a small
inclination, the operation is similar to that described above in
connection with a normal starting. Because the vehicle load dNe/dt
is small, a data group having an increased value of dVs/dt is
specified during the segment l=0. Similarly, during the segments
l=1, 2, . . . , an increased value of e caused data groups having
an increased value of dVs/dt to be specified, thus allowing an
early achievement of e=1 by the clutch control. When the slope is
steep, upon starting, the vehicle begins running without any
application of the engine power thereto. Thus, the decision
"e.ltoreq.0.1?" at the lower end of FIG. 6a is exited through NO,
whereby the clutch control transfers to the engine brake control
flowchart shown in FIG. 6h. During the engine brake control, CPU 91
determines an actual slip rate e which is less than 1 to be a
starting on a slope (since e>0.1), skipping over the segment l=0
and transferring to the clutch control shown in the later part of
FIG. 6d and to the segment l=1 and subsequent segments in FIG. 6e.
In other words, when the slip rate of the clutch (No/Ne) increases
above a given value, the control segment l=0 is skipped. When the
engine brake is applied, T.theta..ltoreq.5%, and hence the
flowchart transfers from the third step of FIG. 6e to the step
.circle.3 of FIG. 6a, where the clutch is turned off. CPU 91
calculates the actual slip rate, and if it finds that e>1,
allowing the application of the engine brake, CPU 91 stores "10" in
the register i for 1.ltoreq.e.ltoreq.2, determining that the
vehicle load is negative and has a small absolute value, and stores
"11" in the register i for 2<e, determining that the absolute
value is high. Subsequently, the CPU 91 reads the content of the
registers i, j, K and l to define an address, which is used to read
clutch controlling data Vsx from either ROM 92 or 93. This data is
stored in the output register Cp and is also applied to the output
ports O.sub.2 to O.sub.12. Before entering the flowchart shown in
FIG. 6h, the registers i, j, K, l and Cp are cleared as a result of
the final step e.ltoreq.0.1?=NO in the flowchart of FIG. 6a, so
that i=10 or 11, K=1 and l=0 at this time. When having read data
corresponding to K=1, CPU increments K by one for each subinterval
of 0.05 sec to read data out of ROM, which data is used to update
the content of the register Cp and to update the data applied to
the output ports O.sub.2 to O.sub.12. The value of K is monitored,
and when K=33, or when 0.05.times.33=1.65 sec has passed since the
initiation of engagement of the clutch, the clutch control is
complete in any engine brake control mode (since Vsm is applied to
the output ports O.sub.2 to O.sub.12), and thus the CPU returns to
reading the shift lever position Sp. If the shift lever position is
neutral N, the flowchart transfers to the step .circle.3 of FIG.
6a. If there is no change in the shift lever position, both the
throttle opening T.theta. and the rotational speed of the engine Ne
are read, and Vsm (e=1) is not changed so long as
T.theta..ltoreq.60% and Ne.ltoreq.900 rpm or T.theta.>60% and
Ne.gtoreq.1200 rpm. If T.theta..ltoreq.60% and Ne<900 rpm or if
T.theta.>60% and Ne<1200 rpm, there is a likelihood that an
engine stop may occur, thus requiring a transfer to the
disengagement of the clutch under the step .circle.3 of FIG. 6a.
Thus, when the engine brake is applied, a region (OFF) as indicated
in FIG. 8e is designated to disengage the clutch.
(4) Clutch control when repeating a forward and a reverse mode:
When getting the vehicle out of a mire, when riding past an
obstacle on the road or turning a narrow T shaped curve, the clutch
is repeatedly switched between the forward and the reverse mode
(drive D and reverse R) within a short interval, giving rise to the
occurrence that the shift lever position may assume the drive D
position when the output shaft of the clutch is rotating in the
reverse direction or the shift lever position may assume the
reverse R position when the output shaft is rotating in the forward
direction. At this time, the CPU 91 determines if the direction of
rotation of the driven shaft of the clutch and the preset shift
lever position is similar or dissimilar in accordance with the
direction of rotation signal, the output from the decision circuit
78 applied to the input port I.sub.16 and indicative of the
direction of rotation of the driven shaft of the clutch, and the
shift lever position Sp, contingent upon the requirement that the
step "No=0?" of FIG. 6b exits through NO or the driven shaft is in
rotation. When switching between the forward and the reverse mode
within a short interval, or when the direction of rotation of the
driven shaft of the clutch is opposite from the preset shift lever
position, the clutch ON control is initiated after waiting for a
reduction in the rotation of the driven shaft for 0.2 sec.
Consequently, where the slip rate (Vsx) of the clutch 30 is
normally to be controlled as indicated by a solid line in FIG. 8c,
the engagement of the clutch is delayed by 0.2 sec as indicated by
dotted lines if the driven shaft of the clutch is rotating in the
opposite direction from that established by the shift lever
position. This prevents an overloading of the engine and an engine
stop.
(5) Manual temporary clutch activation:
When the flipflop FF1 is set in response to the closure of the
manual switch 14, the input port I.sub.25 assumes a high level or
"1". During the clutch control in the segment l=1 and subsequent
segments (continuing from the bottom of FIG. 6d to FIG. 6g), the
CPU 91, after presetting i and j, reads the input port I.sub.25
("I.sub.25 ="1" ? of FIG. 6f), and if I.sub.25 is equal to "1", it
establishes a data updating timing tt to be 0.1 sec. As a result,
whenever I.sub.25 is equal to "1", the value of K is incremented
for each interval of 0.1 sec. In other words, a single segment
(l=1, l=2, . . . ) encompasses 0.8 sec. When I.sub.25 is equal to
"0", the value of tt is chosen to be 0.05 sec, and hence the value
of K is incremented for each subinterval of 0.05 sec so that a
single segment corresponds to 0.4 sec. Consequently, whenever
I.sub.25 is equal to "0", the slip rate of 1 (Vsm) is achieved
within a time interval of t.sub.1 while whenever I.sub.25 is equal
to "1", the slip rate of 1 (Vsm) is achieved within a time interval
of 2t.sub.1, doubling the temporary clutch activated time. Hence,
when the traffic on the road is congested to result in a reduced
spacing between adjacent vehicles, the driver may start after
temporarily closing the manual switch 14. The flipflop FF1 which
produces I.sub.25 ="1" is reset in the flowchart of the engine
brake control shown in FIG. 6h after once achieving e=1 (Vsm) for
the clutch in the engine brake mode. This resetting operation takes
place by CPU 91 applying "0" output on the output port O.sub.1.
Accordingly, the clutch ON control having an increased length of
temporary clutch activation takes place after momentary closure of
the manual switch 14 until the engine brake is applied or until the
vehicle has get out of the congested traffic condition and is
accelerated and subsequently decelerated by the engine brake.
The above operations (1) to (5) can be summarized as follows:
(a) The clutch ON control is initiated when establishing the drive
D or reverse R shift lever position and reaching the rotational
speed of the engine Ne.gtoreq.900 rpm.
(b) At the initiation of the clutch ON control, the actual slip
rate e which is derived when establishing the slip rate e=0 for the
clutch enables a discrimination between a condition in which the
engine power is required to drive the vehicle and another condition
in which the engine power is required to brake the vehicle.
(c) Under the condition that the engine power is required to drive
the vehicle, there is an instance in which the first segment l=0 is
skipped over and the clutch ON control may begin from the second
segment l=1 when the actual slip rate e is greater than 0.1, and
another instance in which the clutch ON control is to be started
from the first segment l=0 whenever the actual slip rate e is equal
to or less than 0.1. In the former instance, the clutch ON control
in the second segment l=1 which is described under the paragraph
(e) below is immediately entered.
(d) When the clutch ON control is to start from the segment l=0, a
reduced value of the actual slip rate e requires that an oil
pressure which achieves a low level of engagement of the clutch
(Vs2) be applied to the clutch in order to allow the load to be
detected, followed by the detection of a reduction in the number of
revolutions of the engine Ne. After detecting a reduction in Ne,
dNe/dt is detected in order to determine the load on the vehicle
such as the weight, the inclination of the load or the like. The
throttle opening T.theta. is used to determine the engine power.
The combination of the vehicle load and the engine power specifies
a particular data group (Vsx=f(t)) having a proper clutch on change
rate (dVs/dt) in the first segment l=0. The clutch controlling
signal Vsx is changed at a time subinterval of .DELTA.T=0.05 sec.
In the segment l=0, ##EQU1## After proceeding through the segment
l=0, the clutch ON control enters the second segment l=1.
(e) During the clutch ON control for the second segment l=1, the
actual slip rate e is utilized as indicative of the vehicle load,
and the throttle opening is utilized as indicative of the engine
power in the same manner as in the first segment. These specify a
particular group of clutch controlling data Vsx=f(t) having a
proper clutch ON change rate (dVs/dt) for the second segment l=1.
The clutch control signal Vsx is changed at a time subinterval of
.DELTA.t=tt sec. In the second segment l=1, ##EQU2## After
proceeding through the segment l=1, the clutch ON control in the
third segment l=2 is entered. This takes place in the similar
manner as during the segment l=1. A similar clutch ON control is
repeated for the segments l=3, 4, . . . . However, during any
segment beginning with the segment l=0, if the clutch control
signal reaches Vsm which specifies that e=1, the clutch controlling
data ceases to be updated, and the shift lever position Sp, the
actual slip rate e and the throttle opening T.theta. are read at a
time interval of ##EQU3## (or ##EQU4## where I.sub.25 ="1"
specifying a temporary clutch activation). When Sp indicates the
neutral N position, the control returns to clutch OFF (specifying
e=0) or the paragraph (a) mentioned above, and when
T.theta..ltoreq.5%, the decision of the condition mentioned above
under the paragraph (b) is made.
(f) If it is determined under the paragraph (b) that the engine
power is required to brake the vehicle, the clutch ON control which
enables the application of the engine brake is performed. In this
instance, the clutch proceeds from its non-engagement to its
complete engagement within a reduced time, and after the complete
engagement is achieved (Vs=Vsm), the shift lever position Sp, the
throttle opening T.theta. and the rotational speed of the engine Ne
are continuously monitored. Whenever they indicate a condition
during which the engine brake cannot be applied, the control
returns to the clutch OFF (specifying e=0) to recycle to the
paragraph (a).
(g) If the direction of rotation of the driven shaft of the clutch
differs from that specified by the shift lever position Sp under
the paragraph (d), an oil pressure which achieves a low level of
engagement of the clutch (Vs2) is applied with a given time delay
of 0.2 sec.
(h) If during the clutch ON control for the segment l=1 and
subsequent segments which was mentioned under the paragraph (d),
the flipflop FF1 is set (I.sub.25 ="1"), .DELTA.t=tt=0.1 sec and
the single segment of ##EQU5## are chosen, doubling the time
required from e=0 (Vs=Vs2) to e=1 (Vs=Vsm) to be doubled as
compared with the time required when the FF1 is reset (I.sub.25
+"0"). In other words, the temporary clutch activation period is
doubled. The flipflop FF1 is set by a momentary closure of the
manual switch 14, and is reset by Vs=Vsm during the application of
the engine brake.
As discussed above, in the described embodiment, a particular group
of clutch controlling data is specified from the initiation of the
clutch ON control by a combination of the number of revolutions of
the engine (Ne), the actual slip rate (e), the vehicle load
(dNe/dt) and the engine power (T.theta.). Subsequently, the
particular group of clutch control data is updated in accordance
with the vehicle load (actual slip rate e), the engine power
(T.theta.) and the lapse time (l) of the clutch ON control, at a
given time interval ##EQU6## Within this time interval ##EQU7## the
clutch ON controlling data is updated at a subdivided time interval
or subinterval of .DELTA.t. Accordingly, the slip rate of the
clutch is properly controlled and changes smoothly and rapidly in
accordance with the driving condition of the vehicle, the traffic
condition on the road and the lapse of the time. This eliminates
any sudden change in the speed of the vehicle and also eliminates
an engine blow or stop, assuring a very smooth automatic clutch ON
control. Similarly, the application of the engine brake is
automatically, smoothly and rapidly controlled. No engine blow or
stop is caused by frequently switching the shift lever position
between the drive D and the reverse R position within a short
interval as when getting the vehicle out of a mire, moving past an
obstacle on the road or turning through a narrow T curve. A
temporary clutch activation over a prolonged period of time is
enabled by a manual operation as when going through a congested
traffic condition.
While an embodiment of the invention has been shown and described
above, it should be understood that the invention can be carried
out in other manners as well. By way of example, the throttle
opening sensor 12 may be replaced by a potentiometer, contact
electrode or absolute rotary encoder employing a photo-interrupter,
and if required, may be combined with an A/D converter for purpose
of digital conversion. The only requirement is that the sensor be
capable of converting a throttle opening or any associated physical
quantity into an electrical signal. The same is true for the
detection of the rotational speed of the drive shaft and the driven
shaft of the clutch. In this instance, a photo-encoder or
tachometer may be used. Alternatively, the pulse counter may be
replaced by an integrating circuit, and the resulting analog speed
signal converted by means of an A/D converter. Also, in the
electronic control system, the microprocessor unit 94 may be
replaced by a combination of ROM and a counter circuit which sets
up an address, with the read-out of data from the ROM being
controlled by means of logical gates, flipflops and counters.
* * * * *